The standard enthalpies of formation Delta(f)H(o) (liq. or cr.) at the temperature T = 298.15 K were measured using combustion calorimetry for benzophenone (A), 1-indanone (B), alpha-tetralone (C), 9-fluorenone (D), anthrone (E) and dibenzosuberone (F). The standard enthalpies of vaporization Delta(v)H(o) or sublimation Delta(s)H(o) of A-F and 5,7-dihydro-6H-dibenzo[a,c]cyclohepten-6-one (G) were obtained from the temperature function of the vapor pressure measured in a flow system. Enthalpies of fusion Delta(m)H of solid compounds were measured by DSC. From the enthalpies of formation of the gaseous compounds of A-G the values of their strain enthalpies were derived and structural effects discussed.